258 lyiAjOR w. s. patton. 



twelve ; in Lmilia sericata (fig. 2, d) seven or eight. In Sarcophaga (fig. 2, e) the anterior 

 spiracle is large, and there may be sixteen or more processes, and the vestibule has 

 many small, clear circular areas. 



I have, I think, now shown that if the characters of the posterior stigmata, 

 cephalophar^mgeal skeleton and anterior spiracles are taken together, the species to 

 which any given larva belongs can be determined with certainty. 



The following key to the larvae of some of the more important myiasis-producing 

 Diptera (exclusive of the Oestridae) will be useful for reference. 



Key for Identification of some of the Larvae of the Myiasis-producing Diptera. 



1 . Larvae with fieshy processes ; posterior spiracles at the end of tubercles or a 



tube. 



(a) Small broad, dirty white larvae about 4 mm. in length, with small pointed 



fleshy processes in pairs on dorsum, increasing in length from before back- 

 wards ; two long fleshy processes at sides of last segment, which is the 

 broadest ; posterior stigmata on brown chitinous tubercles, each with a 

 narrow opening ; movements caterpillar-like 



Aphiochacta xanthina {ferruginea) . 



(b) Similar larvae, with hairy processes A. riifipes. 



(c) Medium-sized to large larvae with long pointed fleshy processes dorsally and 

 laterally, increasing in length from before backwards, with small spines at 

 their bases, shaft and ends bare; body compressed dorso-ventrally; posterior 

 stigmata stalked, consisting of four lobes, each with an opening situated on 

 dorsum of sides of apparent 8th segment . . . . Fannia canicularis, 



(d) Fleshy processes with numerous branches, giving the process a feathery 



appearance . . . . • • • • • • • • Fanma scaiaris. 



{e) Medium-sized to large larvae with long pointed fleshy processes with a small 

 tuft of spines at their apices ; posterior stigmata in cleft at end of apparent 

 8th abdominal segment, consisting of large chitinous plates with broad rims, 

 and three straight slits directed downwards and inwards 



Chrysomyia alhiceps [rufifacies), C. varipes. 



(/■) Large soft larvae ; integument covered with hairs and spines ; seven pairs 

 of short pseudopods on ventral surface ; posterior stigmata situated at the 

 end of a long tube, which can be telescoped or extended at will 



Eristalis, Helophilus. 



\l. Medium-sized to large smooth larvae without any fleshy processes ; posterior 

 stigmata normal, not at the end of tubercles or a tube . . . . . . 2. 



2. Posterior stigmata somewhat D-shaped ; button area situated well within 



the ring ; slits curled. 

 [a] All slits with three convex loops outwards . . Musca domestica and allies. 

 \b) Upper and lower slits with two loops, convex externally ; middle sHt with 

 only one . . . . . . . . • • • • • • Philaematomyia. 



2' . Posterior stigmata large, rounded or o^^al, with straight slits . . . . 3. 



3. Chitinous ring complete and inclosing button area. Calliphora, Lucilia.Cynomyia. 



(For distinctions see drawings of posterior stigmata.) 

 3/. Chitinous ring incomplete . . . . . . . . • • • • . . 4. 



4. Slits all directed downwards and inwards. Chrysomyia, Cochliomyia, Phormia. 



(For distinctions see drawings of posterior stigmata.) 

 Ai Liternal sHts comma-shaped, directed downwards and outwards ; middle 

 slits almost straight down ; outer slits directed downwards and inwards 



Sarcophaga. 



